This invention relates to digital data controlled systems and more particularly to systems for controlling and monitoring an extensive number and variety of machine tools.
With the increasing automation of industry, both in manufacturing and in facilities controlling and monitoring, as well as the ever increasing automation of many aspects of life, both in homes and business offices, there is a constant demand for means for increasing the distribution potential of the central processing unit input/output in order to increase the capability of such central processors to interface effectively with an extensive number and variety of machine tools capable of carrying out automated industry, office and home operations. One traditional approach toward increasing the input/output distribution potential of a central processing system is to use standard centralized multiplexing techniques either directly within the central processor or in an associated centralized data processing subsystem which has an extensive multiplexing potential and responds to instructions from the main central processor applied through a single or double I/O bus by interpreting such instructions and then conducting digital data transactions with the selected remotely located machine tools over one of up to a thousand or more I/O buses which would be required for the multiplexing subsystem to individually communicate with all of the remotely located machine tools interfacing with it.
While such multiplexing systems have been effectively used where there are a limited number of machine tools being monitored and controlled by the central processor or where the machine tools can be located reasonably close to the central processor, such multiplexing systems have been less than fully satisfactory where a great number of machine tools or at least machine tool subfunctions have to be controlled by the central processor or where the machine tools to be controlled are remotely located with respect to the central processor, i.e., at distances exceeding hundreds and even thousands of feet. Some of the shortcomings of the standard multiplexing systems and subsystems in the latter cases are that the data from the multiplexing subsystem has to be transmitted over up to one thousand or more individual data buses over long distances. Thus, signal conditioning (bringing the digital I/O signal from the central processor into a condition to which the machine tool can respond) at a centralized location adjacent to the multiplexing function is impractical since the conditioned signal would then have to travel for considerable distances on its respective bus through a hostile environment where it could be adversely affected by stray noise. This would necessitate individual signal conditioning units either adjacent to or within the machine tool, thereby increasing the expense of signal conditioning.
In any event, even when the signal conditioning is conducted on an individual basis at the machine tool, the problem of running up to one thousand or more individual data buses over long distances becomes very expensive. The hostile environment through which such data buses must run will affect even bilevel digital data on the line and great lengths of expensive coaxial protective cabling has to be used for the numerous data buses.
The prior art has recognized many of these problems, and has to some extent developed systems having remotely located tool controllers functioning under the control of the central processor for controlling tools associated with the tool controllers. However, the operation of such systems with respect to the distribution of data transactions between the central processor and the digital I/O to the machine tool has been slower and less efficient from a digital data processing viewpoint than the aforementioned more expensive multiplexing systems.
In addition, it would be desirable in the art to have a system of tool controllers located near the machine tools and remote from the central processor wherein the tool controller would require minimized data transactions with the central processor.